Berthold Schiemenz

PENTA-COORDINATED CHLOROSILANES: REACTION CHEMISTRY, STRUCTURE AND BONDING

The synthesis and reaction behavior of the penta-coordinated chlorosilanes [C 6 H 4 CH 2 N(CH 3 ) 2 -2]Si(Cl)(R)(R′) [ 3a : R=R′=Cl; 3b : R=R′=CH 3 ; 3c : R=C1, R′=CH 3 ; 3d : R=Cl, R′=CHCH 2 ; 3e : R=CH 3 , R′=CHCH 2 ] are discussed. Compounds 3a–e can be obtained by the reaction of LiC 6 H 4 CH 2 N(CH 3 ) 2 -2 ( 1 ) with stoichiometric amounts of (R)(R′)SiCl 2 ( 2 ) in high yields and give access to a versatile reaction chemistry on substitution of the chlorine atoms by many of the diverse nucleophiles used. Hydrolysis of compound 3d produces oligomeric {[C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)SiO} n ( 4a ), whereas 3e yields the disiloxane {[C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)(CH 3 )Si} 2 O ( 4b ). Alcoholysis of compounds 3d and 3e in presence of NEt 3 affords [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)(CH 3 )Si(OCH 3 ) ( 5a ) or [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)Si(OR) 2 [ 5b : R=CH 3 , 5c : R=C 2 H 5 , 5d : R= i C 3 H 7 ], respectively. Compound 5b can be transferred to the difluorosilane derivative [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)SiF 2 ( 6 ) by its reaction with BF 3 *O(C 2 H 5 ) 2 , while treatment with LiAlH 4 produces the silane [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 2 CH)SiH 2 ( 7a ). Moreover, hypervalent silanes are accessible by the reaction of chloro-functionalized 3d or 3e with LiAlH 4 whereby compounds [C 6 H 4 CH 2 N(CH 3 ) 2 ](H 2 CCH)Si(H)(R) ( 7a : R=H; 7b : R=CH 3 ) are formed in good yields. Metathesis reaction of compounds 3b–e with LiR reagents [R=CCR′, NHC 6 H 2 (CH 3 ) 3 -2,4,6, P(C 6 H 5 ) 2 ] produces [C 6 H 4 CH 2 N(CH 3 ) 2 -2](CH 3 )(R)(SiCCR′) [reaction of 3b or 3e with LiCCR′; 8a : R=CH 3 , R′=C 6 H 5 ; 8b : R=CH 3 , R′=Si(CH 3 ) 3 ; 8c : R=CHCH 2 , R′=C 6 H 5 ; 8d : R=CHCH 2 , R′=Si(CH 3 ) 3 ], [C 6 H 4 CH 2 N(CH 3 ) 2 -2](R)Si(CCR′) 2 [reaction of 3c or 3d with LiCCR′; 9a : R=CH 3 , R′=C 6 H 5 ; 9b : R=CHCH 2 , R′=C 6 H 5 ; 9c : R=CHCH 2 , R=Si(CH 3 ) 3 ], [C 6 H 4 CH 2 N(CH 3 ) 2 -2](H 2 CCH)Si[HNC 6 H 2 (CH 3 ) 3 -2,4,6] 2 [reaction of 3d with LiNHC 6 H 2 (CH 3 ) 3 -2,4,6; 10 ] or [C 6 H 4 CH 2 N(CH 3 ) 2 -2](H 2 CCH)Si[P(C 6 H 5 ) 2 ] 2 [reaction of 3d with LiP(C 6 H 5 ) 2 ; 11 ]. The solid state structures of 3c and 3d are reported. Complex 3c crystallizes in the monoclinic space group P 2 1 / c with a =8.918(5), b =11.557(3), c =12.830(7) A; β =108.17(4)°, V =1256(5) A 3 and Z =4; 3d crystallizes in the monoclinic space group P 2 1 with a =6.625(3), b =8.574(6), c =11.281(8) A; β =88.16(5)°, V =640.5(7) A 3 and Z =2. The central silicon atom in compounds 3c and 3d shows an essentially distorted trigonal-bipyramidal coordination sphere, with the axial positions occupied by the nitrogen donor atom and one chloro ligand. Dynamic 1 H-NMR studies confirm that the same geometry is adopted in solution.

Unusual structures of lithium terphenyl derivatives

Abstract The synthesis, spectroscopic and structural characterization of three new lithium derivatives of terphenyl ligands are reported. These are the mixed lithium alkyl–lithium aryl compound {Li(t-Bu)LiC6H3-2,6-Trip2} (1, Trip=C6H2-2,4,6-i-Pr3), the dilithiated {LiC6H3-2-(C6H3-2-Me-5-t-Bu)-6-(C6H3-2-CH2Li-5-t-Bu)·Et2O}2 (2), and the ether solvated (Et2O)LiC6H3-2,6-(C6H4-4-t-Bu)2 (3). The synthesis of the terphenyl halide precursors for 2 and 3 is also given. The compound 1 resulted from the treatment of 1-IC6H3-2,6-Trip with two equivalents of Li(t-Bu) in hexane. It features the alkyl and aryl (terphenyl) groups bridged by two lithium ions. The lithium ions are further solvated by ortho aryl substituents and methyls of the t-Bu groups. This compound is a very rare example of a mixed lithium alkyl–lithium aryl species. Compound 2 was obtained in low yield from the treatment of 1-BrC6H3-2,6-(C6H3-2-Me-5-t-Bu)2 with two equivalents of Li(t-Bu). The terphenyl ligand was dilithiated by replacement of the bromine and a hydrogen from one of the methyl groups on the ortho aryl substituents. The ether solvated, dimeric, tetrametallic structure illustrated in the Table of Contents resulted. The compound 3 was obtained from the straightforward lithiation of the iodoterphenyl precursor in the presence of diethyl ether and features a lithium ion solvated by two ethers terminally bound to the ipso-carbon of the terphenyl group.

Four-Coordinate Group-14 Elements in the Formal Oxidation State of Zero – Syntheses, Structures, and Dynamics of [{(CO)5Cr}2Sn(L2)] and Related Species

The sodium salts Na2[{(CO)5M}2EX2] (M = Cr, Mo, W; E = Ge, Sn, Pb; X = Cl, I, OOCCH3) react with 2,2′-bipyridine (bipy) to form neutral compounds [{(CO)5M}2E(bipy)] (E = Sn: 1a–1c; E = Ge: 3a; E = Pb: 4). 1,10-Phenanthroline (phen) analogues of compounds 1a–1c and 3a [{(CO)5M}2E(phen)] (E = Sn: 1d–1f, E = Ge: 3b) are as well accessible. The 2,2′-bipyridine ligand in 1 may be formally replaced by two pyridine (py) ligands resulting in [{(CO)5M}2Sn(py)2] (1g: M = Cr, 1h: M = W). The bis-bidentate ligand 2,2′-bipyrimidine (bpmd) is found to coordinate just one [{(CO)5M}2Sn] entity in [{(CO)5M}2Sn(bpmd)] (2b: M = Cr, 2c: M = W). The biimidazolato (biim) ligand binds two [{(CO)5Cr}2Sn] moieties in [{(CO)5Cr}2Sn(biim)Sn{Cr(CO)5}2]2–, 2a. It is shown by 1H-NMR that the pyrimidine entities in these compounds (2b, 2c) are able to rotate by a full 180° turn-around with respect to one another. This process must involve complete de-coordination of at least one of the two nitrogen donors in again at least one of the chelate cycles, the activation energy for this process being around 60 kJ/mol. By 119Sn-NMR spectroscopy of almost all of the tin compounds described it is shown that equilibria between [{(CO)5M}2Sn(L2)] and [{(CO)5M}2Sn(L)] + L exist in all cases. From the temperature dependence of the δ values it is concluded that the activation barriers for this association/dissociation process is below 10 kJ/mol. The structures of all new compounds are documented by X-ray analyses and all compounds are characterized by the usual analytical and spectroscopical techniques.

Lewis-basen addukte monomerer bis(η2-alkin) AgIX-verbindungen (X = BF4oder OSO2CF3)

The reaction of the organometallic 1,4-diyne Me3SiCC[Ti]-CCSiMe3 ([Ti] = (η5- C5H4SiMe3)2Ti) (1) with [AgX]n (X BF4(2a) or OSO2CF3 (2b)) affords {η5-C5H4SiMe3)2Ti(CSiMe3)2}AgX (X = BF4 (3a) or OSO2CF3 (3b)) with 85% yield. The (η2-CCSiMe3)2AgX building in 3 represents a 16-electron complex fragment and the silver atom has a trigonal planar geometry. The reaction of 3 with Lewis bases L leads to the formation of (η5-C5H4SiMe3)2Ti(C CSiMe3)2Ag[X))L)] (L  THF; X BF4 (4), (LP (CCPh)2(CH2Ph) X=OSo2CF3 (5b)) (L = P(OMe)3; X=OSO2CF3 (5c)) (LNCMe, X = BF4 (6a)) (L = NCPh; X = BF4 (6b)) (L = NCPh; X = OSO2CF3 (6c)); with fumarodinitril [{(η5-CH4SiMe3)2Ti(CCSiMe3)2]Ag}2(NCCHCHC N)](OSO2CF3)2 (7) is formed. While 4–6 are 1:1 adducts of 3 and L, 7 has a 2:1 composition of 3 and NCCHCHCN. The (η2-CCSiMe3)2Ag[(X)(L)] building blocks in 4–7 have an 18 electron count and the silver(I) coordination is pseudotetrahedral. All synthesized compounds have been characterized by analytical and spectroscopic data (IR, 1H, 13C and 31P NMR and mass spectroscopy), and {(η5-C5H4SiMe3)2Ti (CCSiMe3)2}Ag[(BF4)(THF)] (4) by X-ray analysis.

Zur Reaktivität von Komplexen [LnMEMLn] (E = Ge, Sn, Pb; Ln = CP′(CO)2Mn) mit den Chelatliganden 1,10-Phenanthrolin, Tetramethylethylendiamin und 1,8-Oxo-Chinolat

Abstract The compounds [CP′(CO) 2 MnEMn(CO) 2 CP′] (E = Ge ( 1a ), Sn ( 1b ), Pb ( 1c )) reacts with 1,10-Phenanthroline (Phen) to yield the chelate derivatives [{CP′(CO) 2 Mn} 2 E(Phen)] (E = Ge ( 3a ), Sn ( 3b ), Pb ( 3c )). The structures of the complexes 3a , 3b and 3c are similar to the structures reported for [{Cp′(CO) 2 Mn} 2 E(Bipy)] (E = Ge ( 6a ), Sn ( 6b ), Pb ( 6c )). The reaction of 1c with Tetramethylethylendiamin (TMEDA) gives the Complex [{CP′(CO) 2 Mn} 2 Pb(TMEDA)] ( 4 ). 1b reacts with 1,8-Oxo-Chinolate (O-Chin) to give the anionic chelate derivatives [{Cp′(CO) 2 Mn} 2 Sn(O-Chin)] − ( A5 ). The new compounds are derivatives of Ge, Sn or Pb respectively in their formal oxidation states zero. X-ray diffraction studies of the Na(12-K-4) 2 salt 5 of the complex anion A5 and of 3a , 3b and 3c are described.

Metallorganische schutzgruppen für den aufbau ungewöhnlicher zinn-chalkogen-käfigverbindungen: Thiostannat(II) Sn3S42− und “Zinnoxidhydrat” Sn6(μ3-OH)4(μ3-O)4 als Liganden in RCp(CO)2Mn-Komplexen

Abstract Thiostannates(II) are considered typical solid state compounds. Isolation of the thiostannate(II) Sn 3 S 4 2− as a molecular entity is achieved by a priori protecting the tin building blocks with R Cp(CO) 2 Mn moieties. The cubane-type R Cp(CO) 2 Mn-protected cage molecules [Na-[2,2,2]Kryptand][{(Cp★(CO) 2 MnSn) 3 S 4 }Na(THF) 3 ] ( 1a ) and [{(Cp(CO) 2 MnSn) 3 S 4 }Mn(THF) 3 ] ( 1b ) have been prepared and fully characterized. As an example of a R Cp(CO) 2 Mn protected rhombic dodecahedral cage molecule [(Cp★(CO) 2 MnSn) 6 (μ-O) 4 (μ 3 -OH) 4 ] ( 2 ) has been obtained. X-ray analysis of 2 shows that the Sn 6 (μ-OH) 4 ] cage of the formal “tin-oxide-hydrate”, “Sn 3 O 3 ·H 2 O”, acts as a ligand towards six Cp★(CO) 2 Mn units via the stereochemically active “lone-pairs” at the tin(II) centres.

Donor-funktionalisierte Alkinyle von Titan(IV), Kupfer(I) und Silber(I); Festkörperstrukturen von [Ti](CCCH2NMe2)2 und {[Ti](CCtBu)2}CuCCCCC2H5

Abstract The preparation of numerous donor-functionalised acetylides with Ti(IV) and/or Group II transition metals is described. The reaction of [Ti]Cl2 (1) {[Ti]=(η5-C5H4SiMe3)2Ti} with two equivalents of LiCCR1 [2a: R1=CMeCH2; 2b: R1=C6H4CN-4; 2c: R1=CH2NMe2; 2d: R=C5H4N-4] affords the bis(alkynyl)titanocenes [Ti](CCR1)2 [3a: R1=CMeCH2; 3b: R1=C6H4CN-4; 3c: R1=CH2NMe2] in good yields. While by treatment of 1 with 2d in a 1:2 molar ratio only non-characterisable products are formed, the use of [Ti](Cl)(CH2SiMe3) (4) produces [Ti](CH2SiMe3)(CCC5H4N-4) (5) in excellent yields. Monomeric, donor-functionalised copper(I) acetylides of general type {[Ti](CCR1)2}CuCCR3 [R1=tBu, 7a: R3=CCCH2CH3; 7b: R3=CMeCH2; 7c: R3=C6H4CN-4; R1=SiMe3, 7d: R3=CMeCH2; 7e: R3=C6H4CN-4] are accessible by (i) the reaction of {[Ti](CCtBu)2}CuSC6H4CH2NMe2-2 (6) with equimolar amounts of 2a–2c or (ii) treatment of the monomeric copper(I) methyl {[Ti](CCR1)2}CuCH3 (8a: R1=SiMe3, 8b: R1=tBu) with HCCR3 [9a: R3=CCCH2CH3, 9b: R3=CMeCH2, 9c: R3=C6H4CN-4] in a 1:1 molar ratio. The reaction chemistry of these complexes towards selected transition metal compounds is described. The bis(alkynyl)titanocenes 3a–3c produce with MLn {10a: MLn=CuCl; 10b: MLn=CuI; 10c: MLn=[Cu(CH3CN)4][PF6]; 10d: MLn=AgBF4; 10e: MLn=Ni(CO)4} the heterobimetallic tweezer complexes {[Ti](CCR1)2}ML [R1=CMeCH2; 11a: ML=CuCl; R1=C6H4CN-4; 11b: ML=CuCl; 11c: ML=CuI; 11d: ML=Ni(CO); R1=CH2NMe2; 11e: ML=CuPF6; 11f: ML=AgBF4]. In complexes 11a–11f an early and a late transition metal centre [e.g. Ni(0)] are linked via the corresponding R1CC ligands of the organometallic π-tweezer complexes. For complexes 11e and 11f a dynamic behaviour is observed in solution. The solid state structures of 3c and 7a are reported. Both compounds crystallise in the triclinic space group P 1 . They exhibit features that are characteristic for this class of complexes: (i) a tetrahedral environment around the Ti(IV) of 3c and 7a, (ii) a lengthening of the CC triple bonds upon η2-coordination to the transition metal complex fragment CuCCCCC2H5, (iii) a trans-deformation of the TiCCtBu unit, and (iv) a reduction of the bite angle CCCTiCCC for 7a.

Nucleophile und oxidative addition von SR-bausteinen an heterometallacumulene

Abstract The dimetallaplumbacumulene complex [Cp′(CO) 2 MnPbMn(CO) 2 Cp′] ( 1 ) reacts with NaSMes to give the product of an oxidative addition process [{Cp′(CO) 2 Mn}Pb(SMes) 3 ] − ( A4 ). The “inidene” compound [{Cp′(CO) 2 Mn} 2 Pb(SMes)] − ( A3 ), which is an intermediate in this reaction, has not been isolated. The analogous tin compound [{Cp′(CO) 2 Mn} 2 Sn(S t Butyl)] − ( A12 ) has been obtained from the reaction of [Cp′(CO) 2 MnSnMn(CO) 2 Cp′] ( 10 ) with LiS t Butyl. The structures of the (Na 2,2,2-Crypt.) salt 4 of A4 and of the (Lithium 2,1,1-Crypt.) salt 12 of the anion A12 have been determined by X-ray methods.

NOVEL INTER- AND INTRA-MOLECULAR DONOR-STABILIZED 1-METALLA-2-SILA-1,3-DIENES

The synthesis of the inter- and intra-molecular donor-stabilized 1-metalla-2-sila-1,3-dienes Cl(H2CCH)SiMLn·OP(NMe2)3[MLn= Fe(CO)4 3a, Cr(CO)5 3b], Ph(PhHCCH)SiFe(CO)4·OP(NMe2)3 3c and (C6H4CH2NMe2-2)(H2CCH)Si MLn[MLn= Fe(CO)4 6a, Cr(CO)5 6b] is described; the X-ray structures of compounds 3c and 6b are reported.

“Iniden”-Komplexe: Ausweitung einer isoelektronischen Reihe auf die dritte Hauptgruppe

Abstract The reaction of K2[Cr(CO)5] with InCl3, followed by addition of [Bu4N]Br, gives {[(CO)5Cr]2InBr}2- (1), that can be isolated in good yield as its tetrabutylammonium salt. Similarly, the reaction of K2[Cr(CO)5] with TlCl3, after metathesis with [Bu4N]Hal, gives {[(CO)5Cr]2TlHal}2- (Hal  Cl, Br, I; 2a-c) in yields of around 60%. X-ray analyses show trigonal planar coordination of the bridging elements, In (1) and Tl (2), in all products. Short InCr (266 pm, 1) and TlCR (268 pm, 2) bond distances indicate substantial shortening by π- interactions. Compounds 1 and 2 thus extend the series of “inidene” complexes to compounds with third main group bridging elements.